The present invention is in the field of the hydraulic control valves and more specifically it is concerned with a 3-way control valve of the type having a single control chamber and which is suitable for use, for example, as a flushing valve. The present invention aims at an improvement of such valves.
A 3-way control valve is typically used in a pressurized liquid line, for opening or closing one or two outlets, responsive to a control signal or depending on flow conditions of the pressurized line. e.g. pressure. Such a valve, may be used, for example, as a back-flushing valve fitted on a supply line and connected in series to a filtering device. In the normal course of operation, when an inlet chamber of the valve is pressurized and a control chamber of the valve is vented, the valve is in an open position allowing flow towards a first outlet chamber (e.g. towards the filtering device) with a second outlet chamber being in a closed position. However, when the inlet port is not pressurized and the control chamber is pressurized, then the valve will close to a position allowing back-flow in a direction from the first outlet towards the second outlet. Typically, the second outlet will be a flushing outlet as known in the art.
A serious problem occurring with 3-way valves, in particular with back-flushing valves, is that essentially high pressures are involves and accordingly strong forces develop within the valve, entailing high mechanical stress in the components thereof. This requires rigid and heavy structures and eliminates the use of plastic materials owing to high moments developing in the construction. In particular, this problem occurs in 3-way valves of the type comprising a control chamber with a diaphragm in which the two outlet ports are essentially aligned and wherein the inlet port is essentially vertical to the outlet ports (at times referred to as non-aligned filtering flow valves).
Owing to the high pressure and forces acting in such valves, the wear of the moving parts is essentially high resulting in that such valves must be frequently serviced and checked for defaults.
It is the object of the present invention to provide an improved 3-way control valve in which the above problems or disadvantages are significantly reduced or overcome.
According to the present invention there is provided a 3-way hydraulic valve comprising a body formed with an inlet port for connecting to a pressurized supply line, a first outlet port for connecting to an outlet line and being in flow communication with the inlet port a gate intermediate the inlet port and the first outlet port, dividing the body into an inlet chamber and an outlet chamber, the body further comprises a second outlet extending from the outlet chamber, and a control chamber fitted with a deformable diaphragm sealingly engageable with the gate so as to prevent flow between the inlet port and the first outlet port and a sealing port associated with the second outlet and comprising a sealing member linearly displaceable between a closed and an open position, said sealing member being attached to the diaphragm whereby when the diaphragm engages the gate said sealing port is open and when the diaphragm disengages from the gate said sealing port is closed, the valve being characterized in that the sealing member is attached to the diaphragm by a linking element having at least two degrees of freedom and whereby disengagement of the diaphragm from the gate entails closing of the sealing port by said sealing member.
By a preferred application of the present invention the second outlet is a flushing outlet whereby back-flushing is performed by flushing liquid flowing in a direction from the first outlet towards the second outlet.
By a first embodiment, the linking element is a rigid link pivotally connected at one end thereof to the diaphragm and at an opposed end thereof to the sealing member. Alternatively, the linking element may be a flexible element such as a strip of material. e.g. plastic or metal. The linking element may also be a cable, a cord or a string made of a variety of materials such as rope, metal, fibers, rubber and elastomers etc.
Preferably, the sealing member is spring biased into sealing engagement with the sealing port when the supply line is not pressurized and when the control chamber is vented.
In order to eliminate friction and reduce forces acting in the valve, the sealing member is restrained from displacement with respect the sealing port accept for linear displacement along its longitudinal axis. By one application, the sealing member comprises radially extending male-female type engagement restricting ribs, one of these being provided on the sealing member and the other at corresponding portions of the sealing port integrally formed with the body or of a sleeve member fixedly retained within the sealing port.
By another application, the sealing member is slidably retained over at least one positioning rod extending parallel to a longitudinal axis of the sealing port.
In order to increase the sealing force of the diaphragm against the gate, an engagement surface of the gate is offset from an axis of symmetry of the diaphragm whereby the surface area of the diaphragm corresponding with the inlet chamber is smaller than that of the outlet chamber. Preferably, the axis of symmetry of the diaphragm is essentially perpendicular to a flow axis of the valve extending between the inlet port and the first outlet port.
By still a preferred embodiment of the present invention a portion of the face of the diaphragm within the control chamber is fitted with a rigid plate element and there is a restraining element extending from a wall of the control chamber, whereby upon disengagement of the diaphragm from the gate, the plate element encounters the restraining element for dampening the displacement and deformation of the diaphragm. Preferably, the plate element performs a combined rolling and sliding motion over a tip of the restraining element. Said restraining element is for example a pin or a rib.